This invention relates to the conversion of nitrogen oxides, such as NO and NO2, and more particularly, to the conversion of nitrogen oxides in the presence of a catalyst supported on a mesh-like structure.
Nitrogen oxides, such as NO and NO2, are undesired by-products found in exhaust gases in various plants such as power plants, including natural gas-fired power plants, waste-to-energy plants, and fuel combustion plants. Nitrogen oxides also may be found in the combustion products of diesel engines.
U.S. Pat. No. 4,280,926 discloses a method for producing a catalytic material for reduction of nitrogen oxides utilizing ammonia as reducing agent. The support material has the shape of a fibrous sheet consisting of non-metallic inorganic fibers mixed with a catalytic active powder. The product can be further treated by impregnation in catalytically active agents. The sheets can be shaped to a honeycomb structure and fixated by a silica solution adhesive.
U.S. Pat. No. 4,416,800 discloses a method for producing a catalytic material. The support material has the shape of a fibrous sheet consisting of non-metallic inorganic fibers mixed with a catalyst carrier powder. The product can be further treated by impregnation in slurry or solution containing carrier materials and catalytically active agents. The catalytic material can be used for:
a) reduction of nitrogen oxides in the presence of ammonia (catalyst: Cu, Fe, V, W and Mo on Al2O3 or TiO2)
b) oxidation of carbon monoxide and hydrocarbons (catalyst: Pt on Al2O3 or TiO2)
In accordance with an aspect of the present invention, there is provided a process for removing at least one nitrogen oxide from a fluid, in particular a gas. The process comprises converting the at least one nitrogen oxide in the presence of a catalyst supported on a mesh-like structure. The mesh-like structure preferably has a porosity of greater than 85%. Preferably the mesh-like structure is fibrous and made of a metal, metal and ceramic or a ceramic.
In a further aspect the mesh-like structure has a porosity of greater than 90%.
In a still further aspect, the at least one nitrogen oxide is selected from the group consisting of NO and NO2 and N2O.
In a further aspect, the at least one nitrogen oxide is selected from the group consisting of NO and NO2 or mixtures thereof. In another aspect, the at least one nitrogen oxide is NO. In another aspect, the at least one nitrogen oxide is NO2. In another embodiment, at least one nitrogen oxide is N2O. In yet another aspect, the at least one nitrogen oxide includes NO and NO2. In yet another aspect, the at least one nitrogen oxide includes NO, NO2 and N2O.
In a further aspect, the catalyst is coated on the mesh-like structure and preferably the coating thickness is less than 30 microns.
In a still further aspect, a process for removing NO from a gas comprises oxidizing the contained NO to NO2 and contacting the NO2 with a metal carbonate, bicarbonate or hydroxide supported on a mesh-like structure, the mesh-like structure comprising a fibrous material of at least one of a metal, metal and ceramic or ceramic and having a porosity of at least 87%.